1. Field of the Invention
The present invention relates to a photoelectric conversion apparatus and a method of driving the same and, more particularly, to a photoelectric conversion apparatus used as an image input means for, e.g., a scanner or an X-ray image pickup apparatus. The photoelectric conversion apparatus is formed by one- or two-dimensionally arraying a plurality of pixels each having a photoelectric conversion device and a switch device. The invention also relates to a method of driving the apparatus.
2. Related Background Art
In recent years, a reading system for a scanner, a digital copying machine, or an X-ray image pickup apparatus has been developed using, a one- or two-dimensional sensor which reads an image with a structure in which photoelectric conversion devices consisting of a semiconductor material represented by amorphous silicon hydride (a-Si) enabling thin film formation and signal processing units are formed on a large-area substrate. Especially, a-Si or polysilicon (poly-Si) can be used not only as a photoelectric conversion material but also as a semiconductor material of a thin film field effect transistor (TFT), so a photoelectric conversion semiconductor layer and a TFT semiconductor layer can be simultaneously formed.
In addition, in a photoelectric conversion apparatus, a capacitor is connected to a signal output line, or a signal output line is provided with a capacitor, and the capacitor is initialized (refreshed).
The photoelectric conversion device also has a capacitor component, and charges stored in the photoelectric conversion device are initialized (refreshed) to prevent an adverse effect on the next signal read.
However, when the voltage of only one electrode of the photoelectric conversion device is controlled using, e.g., a switch, initialization (refresh) can be performed although a time is required for this operation. For this reason, such an arrangement cannot sufficiently meet a requirement for a high-speed operation.